How much chain wear is too much?

[Andrew Swan]

While cleaning my chain tonight, I noticed it was a bit worn, e.g.

- when laid on a table, there was a noticeable difference in length between being fully stretched
and with the ends compressed together (keeping it straight the whole time)
- it can be shaped sideways into about 3/4 of a full circle (sounds bad, huh)

I'm wondering when I should (or more likely, how long ago I should have) replace it - is there
some standard yardstick for telling when a chain is too worn? I've heard of tools that measure
wear by the amount of stretch - are these worth the money, or would it be enough just to measure
the change in distance between a given number of links, in which case how much change (e.g. as a
%) would be too much?

In case it makes any difference, my (road) bike has a 7-speed cluster, triple chainring, and the
chain is the Shimano "narrow" type.

Thanks for any help,

Andrew

 

[Hippy]

"Andrew Swan" <[email protected]> wrote in message
news:[email protected]...
> I'm wondering when I should (or more likely, how long ago I should have) replace it - is there
> some standard yardstick for telling when a chain is too worn? I've heard of tools that measure
> wear by the amount of stretch - are these worth the money, or would it be enough just to measure
> the change in distance between a given number of links, in which case how much change (e.g. as a
> %) would be too much?

"The standard way to measure chain wear is with a ruler or steel tape measure. This can be done
without removing the chain from the bicycle. The normal technique is to measure a one-foot length,
placing an inch mark of the ruler exactly in the middle of one rivet, then looking at the
corresponding rivet 12 complete links away. On a new, unworn chain, this rivet will also line up
exactly with an inch mark. With a worn chain, the rivet will be past the inch mark. If the rivet is
less than 1/16" past the mark, all is well. If the rivet is 1/16" past the mark, you should replace
the chain, but the sprockets are probably undamaged. If the rivet is 1/8" past the mark, you have
left it too long, and the sprockets (at least the favorite ones) will be too badly worn. If you
replace a chain at the 1/8" point, without replacing the sprockets, it may run OK and not skip, but
the worn sprockets will cause the new chain to wear much faster than it should, until it catches up
with the wear state of the sprockets. If the rivet is past the 1/8" mark, a new chain will almost
certainly skip on the worn sprockets, especially the smaller ones.

From the bible: http://www.sheldonbrown.com/chains.html

HTH hippy

 

[Mike]

Andrew Swan wrote:
> While cleaning my chain tonight, I noticed it was a bit worn, e.g.
>
> - when laid on a table, there was a noticeable difference in length between being fully stretched
> and with the ends compressed together

I wouldn't trust that. Measure it stretched, as Sheldon says in hippy's post.

> I'm wondering when I should (or more likely, how long ago I should have) replace it

1) keep it until it starts to jump under load on some gears. By then, you will need a new cassette
though. Less effort for you.

2) if you replace it earlier, (more often) you might save money by a longer cassette life. It
depends on the relative value of chains and gears, I guess. A good idea if you have alloy
chainrings, which wear more easily on an old chain.

 

[Andrew Swan]

Thanks for both answers, they are a big help.

Turns out my chain is stretched by almost 1/8", so I'll take the second poster's advice and just run
with it until it starts misbehaving.

I'll know better with my next chain and gear set!

Thanks again,

&roo

 

[Dclain]

Just so you know, if you replace your chain, be prepared to replace the whole back cluster, possibly
the derail too. I found this out the hard way.

"Andrew Swan" <[email protected]> wrote in message
news:[email protected]...
> While cleaning my chain tonight, I noticed it was a bit worn, e.g.
>
> - when laid on a table, there was a noticeable difference in length between being fully stretched
> and with the ends compressed together (keeping it straight the whole time)
> - it can be shaped sideways into about 3/4 of a full circle (sounds bad, huh)
>
> I'm wondering when I should (or more likely, how long ago I should have) replace it - is there
> some standard yardstick for telling when a chain is too worn? I've heard of tools that measure
> wear by the amount of stretch - are these worth the money, or would it be enough just to measure
> the change in distance between a given number of links, in which case how much change (e.g. as a
> %) would be too much?
>
> In case it makes any difference, my (road) bike has a 7-speed cluster, triple chainring, and the
> chain is the Shimano "narrow" type.
>
> Thanks for any help,
>
> Andrew

 

[Andrew Swan]

DClain wrote:
> Just so you know, if you replace your chain, be prepared to replace the whole back cluster,
> possibly the derail too. I found this out the hard way.

Replacing the whole back cluster makes sense, but why the derailleur as well? Surely it doesn't wear
the same way or to the same extent as the load-bearing components? Or do you just mean the jockey
and tension wheels (the little plastic cogs on the derailleur)?

 

[Mike]

DClain wrote:
> Just so you know, if you replace your chain, be prepared to replace the whole back cluster,
> possibly the derail too. I found this out the hard way.

If that happens, there is no point changing the chain. Put the old one back on, and keep until it
starts jumping. Then replace together with the cluster. But why would you need a new derailer?

 

[chippa]

Yep.....did the same thing, didn't change it until it played up. Play up it did and I ended up in hospital with 4 busted bones. Change it I say.

 

[Mike]

chippa wrote:
> Yep.....did the same thing, didn't change it until it played up. Play up it did and I ended up in
> hospital with 4 busted bones. Change it I say.

What? It was just starting to skip, and you came off ?! How? Riding hard while standing on the
pedals with no cleats or toe-straps??? Or did your chain fail completely?